Low temperature cure coating compositions based on crosslinkable, solvent borne, solution polymers containing activated ester groups, as illustrated by U.S. Patent Application Ser. No. 346,329, filed Feb. 5, 1982, now abandoned and U.S. Pat. Application Ser. No. 377,504, filed May 12, 1982, now U.S. Pat. No. 4,446,250 are known to me. A disadvantage of a coating composition of this type is that coatings must be applied within minutes of mixing to obtain high gloss in pigmented systems.
Also known to me is a prior invention disclosed and claimed in copending application U.S. Ser. No. 529,235, filed Sept. 6, 1983, in the names of D. A. Ley and S. Cady, and directed to a low temperature cure coating composition with improved pot life. This coating composition is based upon an activated ester group-containing, solution polymer and a hemiaminal. The hemiaminal is formed from a volatile ketone and a crosslinking agent having nucleophilic primary amine groups. However, this work is directed to a clear coating composition.
The activated ester group-containing solution polymer based clear coating compositions, either with or without a hemiaminal, yield coatings having good gloss. However, the addition of pigment--e.g., TiO.sub.2 --to nonhemiaminal coating compositions of such type results in substantially increased viscosity with a correspondingly short pot life. Such compositions in turn yield coatings with hazing problems which result in a significantly decreased gloss of the coating.
Hence, there has existed a continuing need for a low temperature cure, pigmented coating composition, based upon activated ester-group containing solution polymers, that provide coatings whose gloss is (a) as good as the corresponding unpigmented (clear base) composition, and (b) significantly better than pigmented compositions not containing a hemiaminal. Therefore, the provision of such a pigmented composition would constitute a significant advance in the art.